Low pressure steam laundry drying machine



G. PERLOFF March 16, 1965 LOW PRESSURE STEAM LAUNDRY DRYING MACHINE 2 Sheets-Sheet 1 Filed Sept. 28, 1961 FIG] FIGZ

INVENTOR.

F IL R E P D L A R E G G. PERLOFF March 16, 1965 LOW PRESSURE STEAM LAUNDRY DRYING MACHINE Filed Sept. 28, 1961 2 Sheets-Sheet 2 as '24 2o Fl G4 INVENTOR.

GERALD PER OFF United States Patent 0 3,173,767 LOW PRESSURE STEAM LAUNDRY DRYING hlAtlHlNE Gerald Period, Rocirville (Centre, N.Y., assignor to international Dryer orporation, Westhuly, Long Island, N.Y., a corporation of New York Filed Sept. 28, 1961, Ser. No, 114L436 3 Claims. (Cl. 34-82) This invention relates to a method and means for drying clothes, and more particularly to a drying machine utilizing low pressure steam as the heating medium.

For nearly a quarter of a century, commercial clothes dryers have utilized high pressure steam or gas as the heating medium in their equipment. The use of gas is expensive and the use of high pressure steam has many disadvantages. Numbered among these are the need for an expensive steam plant, utilizing expensive, stronger and more durable metals, the need for safety devices which are expensive, and under safety regulations the need for an attendant present at all times for controlling the steam plant and for taking safety measures in case of rupture of a steam line or boiler.

Previous attempts to use safer, and less expensive, low pressure steam have failed for several reasons. In the first place, the low pressure is insuificient to rapidly force the steam before cooling through conventional heat exchangers which normally utilize a plurality of coils, as many as thirty or more all connected in series. Accordingly, the air forced over the coils in the heat exchanger is not heated to an adequate clothes drying temperature. Attempts to modify design of the heat exchangers alone have proved unsatisfactory, because without proper systems of air deflectors and baflies it was found impossible to obtain suflicient air at the proper temperature to adequately dry the clothing.

To solve these problems, in the desire to utilize low temperature steam having a pressure of 15 p.s.i.g. or less as compared to the lO0l25#/square inch of ordinary steam driers, the present invention utilizes a special heat exchanger having a plurality of steam coils connected in parallel by inlet and outlet headers. Each coil comprises no more than 4 parallel sections connected by loops so that the length of each passage of the steam in the exchanger is relatively short, and the steam coils being arranged with the parallel sections in substantially vertical planes permit the lowest section to retain practically the same temperature and pressure as the uppermost section. Each of the steam coils has aflixed to its surface thin closely spaced heat conduction and radiation plates forming a multiplicity of laminar paths for air drawn downwardly in substantially vertical directions through the heat exchanger. The exchanger is supported on a special support and air deflector which forms a passage for the heated air toward the clothes receiving drum and some at least of whose sides are inclined inwardly to restrict the area of the passage so that eddy currents are formed redirecting a portion of the air into the laminar spaces between the heat transfer plates. This structure achieves a high rate of heat transfer, increases the Reynolds number for the air flow, reduces boundary layer efiects, and increases the time in which part of the air is subjected to heat from the steam in the coils causing a still better heat transfer rate. In addition bafiles are provided completely around the perforated drum containing the clothing to be dried having an air inlet which, considering the number and size of perforations in the drum, is made to have an effective air passage area less than the total cross sectional area for air flow in the laminar air paths in the heat exchanger. This, again, slows the passage of air and insures that the heat exchanger support and air deflector will redirect a portion of the air back to the heat ex- 3,l?3,?67 Patented Mar. 16, 1965 changer in the form of eddy currents between the laminar heat transfer plates. A drier thus constructed has been, found by experience to have a lower operating cost than any available commercial drier. For example, one hour drying time with a low pressure steam device according to the invention costs approximately 12, whereas high pressure steam costs approximately 15 and natural gas as the heating medium costs 18. Other types of gas are even more costly. A device according to the invention has been found to yield a suitable air temperature in the drum or approximately 180 F. This is more than adequate to dry clothes without scorching the same.

Bearing in mind the advantages of utilizing low pressure steam and the disadvantages of conventional high pressure steam and gas driers described above, a primary object of the present invention is to provide a clothes dryer which will operate at steam pressures below 15 p.s.i.g. and provide an effective temperature of nearly 180 F. in the dryer.

Another object of the invention is to provide a laundry drying machine in which the air is distributed by deflectors, bafiles and similar internal devices so as to effectively utilize the lower temperature of low pressure steam.

A further object of the invention is to provide a clothes dryer of the above described characteristics which will operate at reduced costs, increased safety compared to conventional steam and gas driers and eliminate the problems of an open flame in a gas type clothes drier.

Still another object of the invention is to provide a drier of the above described characteristics which is simple in construction, relatively inexpensive to fabricate and yet effective in operation.

A still further object of the invention is to provide a method for utilizing low pressure steam in the drying of laundry.

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, wherein like reference characters indicate like parts throughout the several figures and in which:

FIG. 1 is a front elevation of a clothes dryer constructed in accordance with the invention and from which the front panels have been removed for revealing internal elements and features;

FIG. 2 is a rear elevation of the drier shown in FIG. 1;

FIG. 3 is an exploded perspective view on a larger scale of the heat exchanger and its air deflector support;

FIG. 4 is a side elevation of the drier shown in FIG. 1 with portions of the side wall removed;

FIG. 5 is a vertical, central, sectional view of the drier; and

FIG. 6 is an enlarged perspective view of the impeller used in the dryer.

Referring now more particularly to the drawing, the numeral 19 generally designates a cabinet which completely encloses the drier except for the opening 12 at the top of the rear side 14. Mounted outside rear wall 14 is an electric motor 16 furnishing power to drive the rotating drum Ztl as well as the impeller blades 40.

The drum 26 is mounted for revolving about horizontal axle 22 and has its cylindrical wall perforated throughout by numerous evenly spaced, small openings 24. Inside the drum are a plurality of partitions 26 which aid in tumbling the clothes during revolution of the drum. The drum is turned through a speed reduction mechanism comprising a pair of small pulleys 28 on the axle of motor 1 6, a pair of larger pulleys 3t) linked by a pair of belts 32, small pulleys 34 fixed to the axles bearing pulleys 30 and a large pulley wheel 36 fixed to the drum axle 22 linked by a pair of belts 33. V

The motor 16 drives blades 40 of a backward wave impellermounted ion the motor .shaft18 extending into the drier cabinet through the rear wall '14 and centrally near the :bottom of the cabinet. The impeller blades are revolved at a high speed and operate in a shroud 42 so as tobe capable of moving 800 cubic feet of 'air per minute against a static head of 1.2 inches of water pressure. The air is moved out of the cabinet in the directions of the arrows shown in FIG. 6 and through the cylindrical outlet 48 which :is normally closed by a door 45 when the drier is not in operation. The door 46 turns on the pivot shaft 44 to permit egress of the air from the cabinet when the drier is in use. The impeller casing 42 is preferably formed by the rear wall 14 of the drier at one side spaced from .an opposite wall of the casing '42 by distance slightly greater than the width of the impeller blades 40. A circular opening 43 is formed at one end of the inside wall of the impeller shroud 42 to admit entrance of air being evcuated by the impeller and the circularzduct 48 passes through a similarly shaped opening in the rear wall of the cabinet at the other end of the impeller'shroud for exit of such air.

A heat "exchanger of special design is provided in the top portion of the cabinet centrally located above the revolving drum 2t) and designated by the general reference character 50. This exchanger comprises vertical walls 52 forming a rectangular frame and having outwardly disposed projecting flanges 54 and 55 at its top and bottom edges respectively. Through opposite walls of the frame 2 are passed a number of steam coils 56 which are linked'together by loops 58 and 60 outside of the frame 52 at the rear and front of the heat exchanger respectively. Each conduit or coil 56 comprises no more than four parallel horizontal tube sections joined by said loops 58 and 6t) to form a four pass coil and each of the described coils are connected in parallel by means of the inlet header 62 and the outlet header-64 at the rear of the heat exchanger.

'Low pressure steam at -p.s. i.g. or as little as 4-p.s.i.g. is connected to the heat exchange through the short inlet pipe 66 formed at one end 'of the inlet header 62 and after passing through the coils 56 in parallel exits from the heat exchanger through the outlet tube 68 connected at the opposite .end of the outlet header '64. Within the frame 52 each coil 56 of the heat exchanger is provided with a plurality of thin, closely spaced, parallel heat exchange plates 70 whichare arranged to form thin laminar air paths vertically through'the heat exchanger. The plates 70 are soldered, welded or'otherwise suitably'connected to tubes 56 and are adapted to conduct and radiate heat to the air as it is drawn downwardly through the heat exchanger.

Above the drum within the cabinet it? is provided a shelf 72 having a central opening in which is secured the combined air deflector and heat exchanger support 76. This device is best illustrated in FIG. 3 and comprises vertical walls 78 at opposite ends connected by downwardly and inwardly inclined walls 80. From the latter a pair of upwardly projected flanges 82 are extended for seating inside the frame '52 of the heat exchanger and a pair of outwardly extended flanges 84 for supporting the bottom flanges 55 of the heat exchanger. At the bottom of the support 76, on all four edges are outwardly projecting, horizontal flanges 90 which are adapted to be supported by the shelf 72 and are secured Walls extend lengthwise of the support so that air deflected by them passes upwardly into the laminar spaces between the heat transfer plates 70 which are positioned at angles to such walls. In assembly of the drier the heat exchanger 52 is merely seated on the flanges 84, of the support .76 and the upwardly extending flanges 82 of the support fit within the vertical walls of the heat exchanger frame 52 preventing lateral and longitudinal movements thereof. Thus assembled the heat exchanger is positioned directly over the central open ing in the shelf 72.

Extending at least the longitudinal sides 8% of the support 76 are a pair of vertical deflector plates 92 which extend the heated air passage to within a short distance from the drum 29. These plates 92, together with the front and rear Walls of the cabinet and the support'76 define the walls of a continuous passage for conducting heated air from the heat exchanger 59 to the revolving drum 2t). Completely about the drum 2% is a baifle of cylindrical shape '94 with a rectangular opening 93 at its top to permit entrance of the walls 92 and inlet of the air therebetwecn and a rectangular outlet 96 placed atone side of the vertical, central axis of the bafide 94 and toward the front thereof as best illustrated in FIGS. 1 and '4. The outlet 96 extends about two-thirds of the length of the baffle '94 and is aligned for permitting exhaust of air fromthe drum and baffie in a direction toward the left bottomand front of the drier cabinet.

In fabricating the heat exchanger and auxiliary air deflectors and bailies described above, care is taken to insure that the effective area of the air inlet 93 to the baffle 9d and perforated drum 2% is less than the sum of the effective areas of the laminar air paths in the heat exchanger between the heat transfer plates 79. In this way, when a vacuum is set up by the impeller at the bottom of the cabinet, air is sucked through the heat exchanger, baffle inlet 93 and restricted openings 24 into the drum 2%. These successively smaller passageways together with the inclined deflector plates 8% on the heat exchanger support '76 serve to retain and restrict movement of the air and deflect a part of the air upwardly into the laminar air paths between the plates 7% so that additional heat transfer may take place because of the resultant eddy currents. This effect is aided by the right angled mounting of inclined plates 85) with respect to the heat transfer plates '70 and the resultant bouncing of air from plates 3% in a normal direction thereto is parallel to the .air passageways between the plates 7%.

In the bottom of the cabinet is mounted a novel lint screen which with its support is generally designated liiti. This .screen comprises a vertical wall 192 having an opening fitting about the impeller shroud 42 and secured thereto in any suitable manner. Slightly above the impeller is .a horizontally disposed wall Ed t extending from the impeller shroud toward the front of the cabinet. Walls 102 and 194 are joined by triangular side panels 1% whose lower edges are inclined upwardly and forwardly toward the front of cabinet it). These lower edges are inturned to provide tracks 107, PEG. 1 into which is removably slid a flat perforated screen 1&5, thus, as seen from FIGS. 1 and 4, air exiting laden with moisture and lint from the bafile opening 96 passes toward the left bottom and front of the cabinet, turns and moves to the right and under the upwardly and forwardlyinclined lower edges of the walls 1%, and then turns again rearwardly to pass into the impeller opening 43 through the screen 1%. When the impeller is operating the screen is bowed inwardly by the suction, attracting and holding the lint against its under suface. When the impeller :is stopped, screen 195 pops out flat depositing the lint on the floor of the cabinet under the screen. Thus in the normal passage of the air to the drier outlet 43, the majority of lint is captured by the screen 165 and dropped to the bottom of the cabinet from where it may be scooped out upon removal of a lower panel, not shown, at the front of the cabinet 10. Any lint bearing air finding its way to other portions of the bottom of the cabinet is prevented from exiting through the impeller opening 43, there being no entry thereto except through the lint screen 1%.

In operation, with the impeller motor 16 started and with low pressure steam at 15 psig. or less and having a temperature of approximately 248 F. admitted to the exchanger intake manifold 62, air will be drawn inwardly into the rear top opening 12 of the cabinet and downwardly through the laminar paths between the heat transfer plates 'ill in the exchanger 52. The use of heat coils 56 in parallel with each coil not exceeding four horizontal sections enables the low pressure steam to pass through the coils without substantial loss of either pressure or temperature and the lowermost horizontal coil section has substantially the same temperature as the uppermost section. Accordingly, the parallel relationship of the four pass coils and the thin laminar spacing between the heat exchange fins 7% enable a high ratio of heat transfer to take place while the air moves downwardly through the heat exchanger. As the heated air passes downwardly through the support 76 toward the opening in the battle 94, a certain proportion of air is reflected back upwardly because of the restricted nature of the bar'lie opening 93 and drum openings 24, and the inclination of the side walls 3i), and this reflection causes eddy currents in the laminar spaces within the heat exchanger proper. Such eddy currents also aid in obtaining an adequate transfer of heat from the steam to the air passing through the heat exchanger. Once the warmed air has passed into the drum some of it will pass outwardly through the openings 24 in the drum wall and expand into the small space surrounding the drum enclosed by the bafi'ie 94. This movement is also accompanied by reflection from the bafiie of the heated air back through the openings 24 into the drum, and a certain amount of eddying back and forth between the drum and the bafile 94 occurs to aid in the transfer of the warmth from the air to the damp clothing to insure adequate drying of the clothing.

The moisture and lint bearing cool air exiting from the drum and battle E 4 through the opening 96 moves toward the left front corner of the cabinet then generally under the upwardly and frontwardly inclined edges of the walls 16-5, then is turned toward the rear of the cabinet under the wall 104 before passing through the lint screen 195 into the opening :3 of the impeller shroud. This makes for a longer path for movement of the air and retains the air in the drum for transfer of heat to the clothing a proportionately greater amount of time. The numerous changes of direction further insures that all of the exiting air passing into the impeller is substantially lint free with the lint deposited in the bottom or" the cabinet under the lint screen.

It will be apparent from the above description that the described apparatus for the first time provides a method and a means of utilizing low pressure steam to adequately dry clothing with all the resultant advantages which have been previously outlined.

Although a certain specific embodiment of the invention has been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

What is claimed is:

l. A low pressure steam drier comprising a drum having a perforated periphery and rotatable on an axis, means for causing air to move through said perforated drum while the latter is rotating, a battle conforming in shape to and closely surrounding said drum, an air inlet and an air outlet in said baffle, a heat exchanger supported ahead of the said inlet adapted to receive steam at 15 p.s.i.g. or less, said exchanger having side walls defining a frame and including a plurality of steam conduits each comprising a tube having no more than four parallel sections supported by opposite walls of said frame and con nected in series by loops, an inlet manifold connecting one end of each of said conduits, an outlet manifold connecting the other end of each of said conduits to provide steam paths in parallel, each conduit having substantially the same low inlet and outlet steam pressures, a plurality of closely spaced heat transfer plates mounted on said conduits arranged to provide laminar paths for air flow in the heat exchanger past said conduits and parallel to the side walls of the frame of the exchanger, and a passage connecting said heat exchanger to said baffle air inlet, at least a pair of the walls of said passage being in planes at right angles to said transfer plates and inclined inwardly to redirect heated air back to said laminar paths and to restrict the air passage connecting the heat exchanger to the bafile air inle the effective total cross sectional area of the perforations in said drum underlying said bafi le air inlet being less than the effective total cross sectional area of said laminar air paths formed by the heat transfer plates and conduits in the heat exchanger.

2. A low pressure steam drier according to claim 1 wherein said heat exchanger walls are vertically disposed and provided with outwardly extending support flanges, said pair of walls of the passage connecting the heat exchanger to the bathe air inlet having upward vertical extensions which fit between and adjacent to corresponding walls of the exchanger frame and horizontal extensions supporting said flanges and a plurality of vertical deflector plates extending downwardly from the walls of said air passage through said batlle inlet to points spaced immediately adjacent but Without touching said drum.

3. A drier according to claim 2 wherein said drum is rotatable on a horizontal axis, said heat exchanger being seated above the drum and together with said air inlet to the baflle being arranged centrally over the drum, said balile outlet being disposed below and at one side of the drum axis, said means for causing air flow including a backward wave impeller mounted centrally below said drum and encased in a shroud having anair outlet at one side in combination with a lint screen preventing entrance of lint to said impeller shroud, said lint screen comprising a vertical wall adjacent said impeller shroud and having an opening communicating therewith, a substantially horizontal top wall at approximately the level of the top of the impeller, a pair of triangular shaped side walls, and a perforated wall slideably and removably supported by the edges of'said triangular walls.

References (Iited in the file of this patent UNITED STATES PATENTS 1,213,999 Balzer Ian. 30, 1917 1,765,628 Staley June 24, 1930 2,110,024 Miller Mar. 1, 1938 2,361,297 Kutsche Oct. 24, 1944 2,595,663 Howland May 6, 1952 

1. A LOW PRESSURE STEAMM DRIER COMPRISING A DRUM HAVING A PERFORATED PERIPHERY AND ROTATABLE ON AN AXIS, MEANS FOR CAUSING AIR TO MOVE THROUGH SAID PERFORATED DRUM WHILE THE LATTER IS ROTATING, A BAFFLE CONFORMING IN SHAPE TO AND CLOSELY SURROUNDING SAID DRUM, AN AIR INLET AND AN AIR OUTLET IN SAID BAFFLE, A HEAT EXCHANGER SUPPORTED AHEAD OF THE SAID INLET ADAPTED TO RECEIVE STEAM AT 15 P.S.I.G. OR LESS, SAID EXCHANGER HAVING SIDE WALLS DEFINING A FRAME AND INCLUDING A PLURALITY OF STEAM CONDUITS EACH COMPRISING A TUBE HAVING NO MORE THAN FOUR PARALLEL SECTIONS SUPPORTED BY OPPOSITE WALLS OF SAID FRAME AND CONNECTED IN SERIES BY LOOPS, AN INLET MANIFOLD CONNECTING ONE END OF EACH OF SAID CONDUITS, AN OUTLET MANIFOLD CONNECTING THE OTHER END OF EACH OF SAID CONDUITS TO PROVIDE STEAM PATHS IN PARALLEL, EACH CONDUIT HAVING SUBSTANTIALLY THE SAME LOW INLET AND OUTLET STEAM PRESSURES A PLURALITY OF CLOSELY SPACED HEAT TRANSFER PLATES MOUNTED ON SAID CONDIUTS ARRANGED TO PROVIDE LAMINAR PATHS FOR AIR FLOW IN THE HEAT EXCHANGER PAST SAID CONDUITS AND PARALLEL TO THE SIDE WALLS OF THE FRAME OF THE EXCHANGER AND A PASSAGE CONNECTING SAID HEAT EXCHANGER TO SAID BAFFLE AIR INLET, AT LEAST A PAIR OF THE WALLS OF SAID PASSAGE BEING IN PLANES AT RIGHT ANGLES TO SAID TRANSFER PLATES AND INCLINED INWARDLY TO REDIRECT HEATED AIR BACK TO SAID LAMINAR PATHS AND TO RESTRICT THE AIR PASSAGE CONNECTING THE HEAT EXCHANGER TO THE BVAFFLE AIR INLET, THE EFFECTIVE TOTAL CROSS SECTIONAL AREA OF THE PERFORATIONS IN SAID DRUM UNDERLYING SAID BAFFLE AIR INLET BEING LESS THAN THE EFFECTIVE TOTAL CROSS SECTIONAL AREA OF SAID LAMINAR AIR PATHS FORMED BY THE HEAT TRANSFER PLATES AND CONDUITS IN THE HEAT EXCHANGER. 